Denture clasp



July 1954 L. E. JOHNSON 2,682,706

DENTURE CLASP Filed Jqn. 12, 1953 INVENTOR. Leonard E. Johnson ATTORNEYPatented July 6, 1954 UNITED STATE t ATENT OFFICE.

This invention relates to prosthetic dentures 8 Claims. (Cl. 32-5) anddental restorations and appliances of the,

type characterized by mounting and positioning means detachablyengageable with a remaining natural tooth, or teeth, adjacent thedenture, restoration, or appliance, and more particularly to thetooth-engageable mounting and positioning a novel and improved dentureclasp susceptible of convenient and repetitious separation from anassociated abutment tooth without deformation or permanent distortion.

A further object of the invention is to provide a novel and improveddenture clasp adapted for secure, operative coaction with a selectedabut- .ment tooth of any particular conformation ap-' propriate for suchuse.

A further object of the invention is to provide a novel and improveddenture clasp amenable to production in fitted relation with a selectedabutment tooth through moderate and facile variation of conventionaltechniques and laboratory practices.

A further object of the invention is to provide a novel and improveddenture clasp that is simple of economical production, characterized bywide utility and pronounced operative advantage, variable in detail withfull retention of primary operative relationships, and reliablethroughout a long life of practical usefulness.

With the foregoing and other objects in view, my invention consists inthe construction, arrangement, and combination of elements ashereinafter set forth, pointed out in my claims, and illustrated by theaccompanying drawing, in which- Figure 1 is a plan view of an exemplarydental restoration as mounted and retained in position of practical useby means of a plurality of clasps typically embodying the principles ofthe invention.

Figure 2 is a side elevation of the arrangement simple dentalrestoration as positioned for practical use through the agency of claspsembodying the principles of the invention.

Figure 4 is a side elevation of the arrangement according to Figure 3.

Figure 5 is a fragmentary, detail elevation, on a relatively enlargedscale, of a representative denture clasp exemplifying the principles ofthe invention.

Figure 6 is a cross section taken substantially on the indicated line 66of Figure 5.

Figure '7 is an elevation, relatively enlarged, of associated elementsrequisite to the production of the improved clasps as interrelated atone stage of such production.

Figure 8 is a vertical section medially of the organization shown inFigure '7.

In the art of prosthetic dentistry it is conventional practice toconstruct partial restorations of diverse particularity as removable andreplaceable units characterized by an embedded, rigid, metallic membercarrying integral end extensions formed as clasps adapted to embracinglyengage with and about sound natural teeth functioning as abutments forthe proper support and detachable positioning of the restoration. Toaccomplish the ends for which they are designed, the clasps associatedwith partial dentures should engage the abutment teeth to which they arefitted without damage to or occasion for deformation of such teeth andin a manner to positively secure and support the denture for use whilefacilitating optional and repetitious removal and replacement of thedenture, all without the presence of tissue-lacerating andfoodentrapping features. The design and production of suitable dentureclasps' has long taxed the ingenuity of technicians with resultssomewhat less than satisfactory, hence the instant invention is directedto the provision of a novel and improved denture clasp susceptible ofproduction with but slight modification of known techniques andprocedures and characterized by enhanced operative properties.

Representative of the many particular restorations wherewith the claspsof the instant invention may be utilized With advantage, Figures 1-4,-

inclusive, illustrate approximate forms of the improvement as developedfor and applied to practical use. ance accomplishing the restoration ofthe four incisors and of the two first molars of a single upper jaw asarranged to be positioned and securely mounted by means of four claspsadapted to engage the second premolar, or bicuspid, and

Figures 1 and 2 show a dental applithe second molar at each side of thejaw, while Figures 3 and 4 show an appliance accomplishing therestoration of the first molar and second premolar, or bicuspid, at oneside of a lower jaw as arranged to be positioned and securely mounted bymeans of two clasps adapted to respectively engage the first premolar,or bicuspid, and the second molar adjacent the ends of the restoration;such appliances being, in and of themselves, conventional and' merelytypical of restorations with which the novel clasps of the invention maybe advantageously employed.

Briefly, in Figures 1 and 2 is shown a rigid; metallic, T-shaped membercomprised fronr a transverse bar and a stem ll perpendicularly,

interrelated to project the stem H anteriorly of" the jaw. The free endof the stem ll. carries;

four incisor restorations i2 thereon disposed to fill the gap betweenthe canines l3 and the free ends of the bar it) individually mount afirst molar: restoration. MI thereon: disposed: to fill the gap: at.each side of the jaw between the second molar I5 and the proximate:second premolar, or:=bicuspi'd-,.la6; The second-molars I5; and secondpremolars l6 of the diSClOSllhB'fl'BPfGSBIlt' soun'd natural teethsuitable to. serve: as abutments? for anchorage of the appliance throughthe agency of end-opening, yoke-type clasps ll integrally and oppositelyoutstanding from free ends- 0f about" the first premolar, or bi'cuspid,20 as anabutment and from'thezposterior end. of which extendsaside-opening, yoke-type clasp I' l" for engagement with: and about: thesecond molar 21' aszanj abutment. Endor side-opening yoke type: cl'aspsin association with and for toothengagement to. position and operativelymount dental?restorationsare, in general, old in the arrangementsillustrated" and in many: other particular dispositions, that whichdistinguishes-the clasps. of the present invention being a novelconstruction. applicable to either or both of-"tha arms. of. a. givenclasp, as hereinafter described; to condition the clasp for automatic,positive,- interl'ockzing' coaction with: the associated abutment toothinan enhancement of" claspgrip readily yieldable to" pressuresappliedior disengagement' ofthe clasp from the tooth,

The essential novelty of the invention, clearly manifest in Figures 5and 6; resides in a contour of the clasp'arm inner'wallsorfacesconformed to and tooverlie the maximum bulgezone of theabutm'enttootlr wherewitli the particular claspis adapted"- to' engage, in the":provisionof a slit intersecting the thickness of eitheror both of theclasp arms longitudinally thereof and extending from an open endadjacent the clasp arm root to a closed end'termination spaced inwardlyfrom the clasp arm tip: along the. line of maximum tooth bulge asevidenced on the clasp arm inner face or wall, and in an inclination ofsaid slit through the clasp arm thickness sucl t as resists; by'v-i'rtueof wedging: action: between the're1ative1yslidable=, adjacentislit'faces, flex-ure' of the slit-freedi clasp: arm portion away from theroot area of the clasp arm. Whileathe. novelties of the invention aremanifestly applicable to side-opening, yoke-type clasps H the generalconstruction represented in plan Figure 3, Figures 5 and 6 show suchnovelties edeveloped in and to modify both arms of an endopening,yoke-type clasp H integrally outstanding from a rigid, metallic, denturebase member or bar 22, such as one end of the bar H). As shown, and isusual practice, the arms 23 and 23' of the clasp ll taper in elevationand in thickness fromimaximumat the I'OOtC-ffthG clasp where it mergeswith the member or bar 22 to minimum at the spaced, free tips 2t and 25,respectively, of said arms, thus to progressively, and, obviously, varythe inherent flexibility of the so-constituted arms. Giving effect tothe principles of the invention, the inner, spacedlyopposedfaces of thearms 23 and 23' are conformably contoured to overlie the zone of maximumbulge characterizing the abutment tooth wherewith the clasp is toicoact,such contouring resulting from; molding or' casting the clasp armsona-ndabout a replica of the actual tooth, as hereinbelow elaborated,and. a slit, 25 for.

the: arm:.23 and 25 forthe arm 23 divides the:

width. and: opens through thethickness of: each of, the clasp arms' in:a disposition longitudinally of: each arm.- determined. at the arm innerface.

by the line'of maximum; inner face concavity, or maximum: tootht bulge,and such as to open through the; root. of: the; arms. at one end; and toterminate at the. other end in spaced relation inwardly from. ther armtip 2 or 24", such" slit disposition resulting in the definition of: anarm finger portion, 26 for the arm 23L'and126? for the arm: 23.,havin'gJa. free end adja'c'ently'underlying. the. root portion of the:associated clasp arm and. a. zone of; attachmentzto. said: arm; notfarremoved from the arm tip where the arm origin-a1 thickness has been:reduced by normal: arm. taper to.-accommodate:aniavailable degree. offiez-rure at the junctionof. the arm finger portion with the arm body.from which said. finger portion is freed for limited lateral relativeswingsby' virtue of the slit just described. The: arm finger'portion 26;or: 26., is' conditioned to engage with its concaved inner faceconf'ormably fitted againstthe inwardly=tapered, or undercut, area ofthe abutment tooth thereby. circumferentiall'y: embraced at' thegingival side. of the tooth line of maximum bulge, thereby. introducingoccasi'on forlat'erall'y' outward swing of the finger portion relativeto the associated. arm whenever the clasp. H, or I1 is shifted' ineither direction axially of the abutment tooth to pass=the gingivalmargin of the clasp across the tooth line of respondingly more resistiveto fiexure from. its

junction with theclasp arm to its-tip and the associated clasp arm 23',or 23, is progressively thinner andcorrespondingly less resistive tofiexure from said junction and to its tip 2 1, or

2 whence it follows that the forces incident to claspshift on the"abutment t'oothwhich tend to swing the finger portion free end laterallyand outwardly relative to the clasp act through said" finger' portion,-and" the associated clasparm to bind the arm tip2'4'; or2'4 in a closeoverlay with the tooth bulge zone thereby engaged and to introduce thenecessity for a slight springing.

apart' o'f the. clasp arms 23." and 23", as. well as outward springingof the finger: portions 25- and- 261,..to p'ermitiseatingofrtherolaspmn,or separation of the clasp from, the abutment tooth. Thus, influencest'ending to unseat the clasp H, or H from coacting relationwith theabutment tooth are resistedby the reluctance of the relatively-stifffinger portion 26, or 26', to yield outwardly and by the consequentlyenhanced grip of the arm tip 24,; or 24', against the abutment tooth inreaction to initial outward swing of the finger portion, whichresistances and reactions serve to retain the clasp in firmly-seatedengagement with the abutment tooth until theunseating influences attaina magnitude adequate to separate the clasp arms 23 and 23' and tosimultaneously flex the associated finger portion, or portions,outwardly beyond the superjacent clasp arm reaches.

While embodiments of the concept characterized'by a slit '25, or 25',formed with its plane transverse ofth'e associated clasparm-perpendicular to a plane tangent to the tooth maximum bulgethroughout the slit length, thus to accommodate relative lateral swingof the finger without resistance other than that deriving from thestillness of the materials employed,'are 'within the contemplation ofthe invention, it is expedient in many clasp constructions, particularlythose developed from more pliant materials and with relatively thinsections, to augment the resistance of the finger 26, or 26', to

outward lateral swing relative to the associated clasp arm through aninclination of the slit transverse plane outwardly and convergently withrespect to the arm and finger gingival margin such as operates todevelop a wedging action between the adjacently-parallel slit faces whenand as the finger issprung outwardly relative to the clasp arm,jsuchinclination of the slit transverse plane being clearly indicated inFigures 5 and 6. With the slit transverse plane inclined as shown anddescribed, it is obvious that resistance to finger portion outward swingincreases as the outward relative displacement of the finger portionincreases and it is likewise manifest that the degree of resistance tooutward finger swing introduced through inclinae tion of the slittransverse plane may be varied and adjusted at the time of claspproduction through appropriate variation in the degree of planeinclination.

Either sideor end-opening, yoke-type clasps incorporating the novelfeatures of the invention in either one or both of the clasp arms aresusceptible of production through the application of but slightlymodified, known techniques; the significant modifications ofconventional techniques requisite for such production being exemplifiedin Figures '7 and 8. In the lastnoted views, the numeral 21 designates acast facsimile or replica, commonly constituted from plaster, of anabutment tooth to and for which a denture clasp is to be fitted, thedevelopment of such replicas and facsimiles as a phase of denture anddenture clasp production being a customary incident of conventionallaboratory procedure, and the numeral 28 designates the wax mock-up, orpattern, representing the ultimately-desired metallic clasp elements aspartially perfected on and in appropriate relation with the facsimile 21in accordance with established practice. Conventionally, the wax pattern28 is completed in simulation and in the use position of theultimately-desired clasp and is then invested, together with its'supporting facsimile 21, within a suitable refractory overlay adapted toreceive and shape molten metal thereto introduced in replacement for thepattern 28. Adapting the conventional techniques indicated to theproduction of the novel and improved clasp hereinabove described, thefacsimile 21 is first marked, in any suitable manner and by anyappropriate means, to clearly indicate thereon the line interjoiningsuccessive points of maximum tooth bulge or lateral protrusion and thearea to be covered by the clasp is then outlined on the surface of thefacsimile as a guide in shaping the pattern 28. Prior to application ofthe pattern 28 material, the line of tooth maximum bulge is scored orincised intothe material of the facsimile 21, as at 29, to groove thefacsimile surface at the location and along the length of the slit, orslits, to be developed in the ultimate clasp arms, and thin sheets orlaminae 30 of smooth, refractory material, such as mica, areedge-engaged in and shaped to follow the length of the scored or incisedgrooves 29 in position to simulate the slits 25, or 25', of the finishedclasp arms. With the sheets or laminae 30 in place on the facsimile 21in widths greater than the clasp arm thicknesses, the pattern 28 isshaped and completed on the facsimile and at both sides of said elements30 with outer edges of the latter projecting beyond the pattern outersurface, whereafter the pattern and the outer edges of the elements 30are invested in a usual manner and the moulding of the metallicreplacement of the pattern is conventionally completed, engagement ofthe element 30 inner edges in the groove of the facsimile 21 and of theelement 30 outer'edges in the refractory investment positioning andimmobilizing said elements during substitution of molten metal for thewax pattern 28. Casting of the metallic clasp having been completed, theinvestment is broken away and the clasp unit is separated from thefacsimile 21 and elements 30, all in an obvious manner, to leave readyfor trimming, polishing, and use the clasp l1 featured by its slits andfinger portions in the operative arrangement shown and hereinabovedescribed and in a transverse inclination of the adjacent slit facesdetermined by the inclination of the elements 30 when and as embedded inand to traverse the material of the pattern 28.

Since changes, variations, and modifications in the form, construction,and arrangement of the elements shown and described may be had withoutdeparting from the spirit of my invention, I wish to be understood asbeing limited solely by the scope of the appended claims, rather than byany details of the illustrative showing and foregoing description.

I claim as my invention:

1. A denture clasp comprising an interrupted, yoke-type band adapted toremovably and replaceably embrace and to conformably overlie the maximumbulge zone of an abutment tooth and an integral finger portion at thegingival side of said band defined by a slit intersecting the bandthickness in registration at its inner edge with the line of maximumtooth bulge and extending at one end through the gingival margin of theband, whereby to condition said finger for independent fiexure relativeto the hand;

2. A denture clasp comprising an interrupted, yoke-type band adapted toremovably and replaceably embrace and to conformably overlie the maximumbulge zone of an abutment tooth, the arm portions of said band beingtapered in width and in thickness from a substantially rigid, commonroot area to their relatively more flexible sesame 7. tips=,.and anintegral finger portion at the gingival side of at least one; of saidarm portions defined; by a slit intersecting theband thickness inregistration at, its inner edge with the lineof maximum tooth bulge,saidslit terminating, in inward-1y spaced relation with the tip of theassociated arm and opening to the'gingivalside'of the arm through theroot area thereof.

3' A' denture clasp. comprising an interrupted; yoke' type band adaptedto removably' and: replaceably embrace and to-conformably overlie themaximumbulge: zone' of an abutment tooth; an integral finger'portion atthegingival side of said band defined by a slit intersecting the bandthickness registration: at its inner edge-with thel-inezot maximum toothbulge, and an inclination of: the slit plane laterally and toward thegingivalsideof the-associated arm productive of wedging' action inresistance to flexure of said finger portion outwardly of its clasp arm.

4; A. denture clasp comprising an interrupted, yoke-type band adaptedtoremovably and replaceably' embrace. andto conformably overlie themaximum. bulge zone of an abutment tooth, the arm portions: of said bandbeing tapered in Width and in thicknessfr-om a substantially rigid,common root area to their relatively more flex-- ible tips,.an integralfinger portion-atthe ging-ival side, ofat least one of said arm portionsdefined by a. slit intersecting the band thickness in registration-atits-inner edge with the line of maximum tooth bulge, said slitterminating in inwardly spaced relation Withthe tipof the associated armand opening to' the gingival side of. the arm through the root areathereof, and an inclination oi the slit plane laterally and toward thegingivalisideof the associatedarm-productive of wedging actioninresistance to fiexure of said finger. portionoutwardlyof its clasp arm.

5s Ina denture clasp-characterizedlby' an inter-- rupted, yokeetype bandadapted. to embrace and to. conformably overlie the maximum bulge zoneofan abutment tooth, means for detachably clamping said bandito and insecure mounted re-- lation. on said tooth, said means comprising anintegral finger portion at the'gingival side of andcapable. Ofindependent. fiexure relative tothe band defined by a slit intersectingthe band-thickness inregistration at its/inner edge. with the: line ofvmaximum tooth bulge and extending at one endithrough the gingival marginof the band 6-. In a dentureiclasp characterized byan-interrupted,yoke-type bandadapted' to' embrace andto: conformably overlie themaximum bulge zone ot an: abutment. tooth means for detachably clampingsaid band to-aml in secure-mounted re=-* lation' on said tooth,saidmeans comprising an integralv finger portion at the gingivalsideofthe band defined by'a slit intersecting the band thickness in inner edgeregistration with the line of maximum tooth bulge, and an inclination orthe slit plane laterally" and toward the gingivalside of the bandproductive: of wedging. action in re'- sistance to fi'exure of saidfinger portion outw ardly of'the band.

'1. In a denture clasp characterized by an interrupted, yoke-type bandhaving. arr-n portions tapered in- Width and thickness fromasubstantially rigid, common root area to-relatively more flexible tipsand inner faces on-saidarmportions contoured to embrace andconformablyoverlie the maximum bulge zone of an abutment tooth; meansfor detachablyclamping said band to and insecure mounted relation on said tooth, saidmeans comprisingan integral finger portion at the gingivalsideof at.least one of said arm portions defined: andconditioned for fiexurerelative to the associated arm portion by a slitintersectingthearmiportion thicknessin inner edge registration withv theline of maximum tooth bulge and opening to the'gingival side of the saidarm portion through the root areathereoi 8. In a. denture claspcharacterized by aninterrupted,. yoke-type bandv having armportionstapered-inwidth and thickness from asubstantially rigid, common rootarea to relatively more flexibletips andinnerv faces. on said. armportions contoured'to embrace and conformably overlie the maximum. bulgezone of an abutment tooth, means. for detachably clamping said band toand in secure mounted relation on. said tooth, said means comprising anintegral. finger portion at the gingival side of at least one ofsaid armportions defined and conditioned for fiexure relative to the associatedarm portion by a slit intersecting the arm portion thickness in inneredge registration with the line of. maximum tooth bulge and opening tothe gingival side of the said arm portionthr'ough the root area thereof,and an inclination of, the slit plane laterally and toward the gingivalside of. the said armportion productive of'wedgin'g action in resistanceto flexure of said finger portion outwardly of the band.

Name Date Aderer May 13, 1924 Number

